July 14, 2024
1 Solar System Way, Planet Earth, USA

Did the Earth lose its protective bubble 2 million years ago?

Graphic showing the Earth surrounded by a large bubble in space, with a box showing the outside of the bubble.
The Earth usually travels inside a protective bubble (the Sun's sphere of influence) called heliosphere. But a new study says that, for a brief period about 2 million years ago, the bubble may have shrunk. The Earth could have been precipitated out of the heliosphere, as shown here as the dark gray bubble on the right, against the background of interstellar space. According to this new research, this change could have exposed the Earth to high levels of radiation and influenced the climate. Image via Merav Opher/ Nature Astronomy/ BU.

Did the Earth ever lose its protective bubble?

The Earth passes through our home galaxy, the Milky Way, inside a protective bubble around our sun. Scientists call this bubble the heliosphere. It's essentially a cavity that surrounds our local star, protecting our planet (and us) from the strongest radiation in the environment. interstellar medium. But on June 10, 2024, a team of scientists saying that, approximately 2 million years ago, the heliosphere could have shrunk. Earth could have been more directly exposed to the interstellar medium. These conditions could have left traces of heavier metals on Earth and could have cooled our climate for a time.

The culprit, scientists said, was a cold cloud in space, made up primarily of hydrogen atoms. That cloud crossed paths with our solar system. In fact, this cloud could have been so dense that it obliterated the sun's protective bubble.

The team published is peer reviewed role in Nature Astronomy on June 10, 2024.

Location, location, location

The Earth has been through numerous ice ages, including the recent one we humans most often think of as the ice Age. It happened during Pleistocene period, between 2.6 million and just 11,700 years ago. To be sure, scientists have proposed many factors that could have contributed to Earth's ice ages. But now, a team of scientists led by Merav Opher from Boston University has proposed another piece of the puzzle.

These researchers believe that it was the sun's location in our Milky Way galaxy that could also have contributed to the last Earth ice age. When our solar system encountered the interstellar cloud (and the bubble shrank), the planets were exposed to harsher conditions beyond the protective heliosphere. Opher saying:

Stars move, and now this article shows not only that they move, but that they undergo drastic changes.

Computer modeling of Earth's history.

Scientists used computer models to look back in time and see where our solar system was in the past. Additionally, the modeling also included something called Local ribbon of cold clouds system. This structure is a chain of immense, dense, super-cold clouds composed mainly of hydrogen atoms. And one of these clouds – the Local cold cloud lynxnear the end of the chain, it could have collided with our solar system.

If that happened, then the sun-protective bubble would have compressed and shrank. In fact, without the sun's protective bubble, Earth and the other planets would have been exposed to radioactive particles. The particles are remnants of exploded stars, such as iron and plutonium. In their paper, the researchers said that increased amounts of iron and plutonium isotopes in the geological record align with this time period. Scientists have found these isotopes in Antarctic snow, in ice cores… and on the Moon.

Scientists said this exposure could have lasted anywhere from a couple hundred to a million years before the return of the protective bubble we live in today. Opher said:

This paper is the first to quantitatively show that there was an encounter between the sun and something outside the solar system that would have affected Earth's climate.

A red ring in the center, partially outside a long yellow spot moving to the right.
Computer-simulated top-down view of the sun and the inner solar system. The red ring represents the Earth's orbit. Yellow is from the sun. heliosphere being compressed from the left side, exposing the Earth to the interstellar medium. Image via Merav Opher/ Nature Astronomy.

More clouds in our future

With this in mind, scientists said it is not possible to know exactly what effect a cold cloud would have had on our solar system. But Earth has likely found others in the past and will do so again in the future.

Now, the team is using data from Gaia mission to look even further back into the past. They are trying to trace the location of the solar system and the cold cloud 7 million years ago. Co-author Avi Loeb from Harvard University said:

Only rarely does our cosmic neighborhood beyond the solar system affect life on Earth. It's exciting to discover that our passage through dense clouds a few million years ago could have exposed Earth to a much greater flux of cosmic rays and hydrogen atoms. Our results open a new window on the relationship between the evolution of life on Earth and our cosmic neighborhood.

Bottom line: A team of scientists said that about 2 million years ago, the solar system may have collided with a cold cloud of interstellar gas and dust, shrinking the sun's protective bubble and exposing Earth to space.

Source: A possible direct exposure of the Earth to the cold, dense interstellar medium 2 or 3 million years ago.

Via Boston University

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